Two samples of double-stranded DNA have been prepared. Nucleotide analysis reveals that sample 1 is found to be 21% A, while sample 2 is 26% G. Knowing this, which of the following statements is true?

Sample 1 has a higher AT content than Sample 2.

Sample 1 is 29% T.

Sample 2 will melt at a lower temperature than Sample 1.

Sample 1 is complementary to Sample 2.

To determine which of the statements is true, we need to analyze the nucleotide compositions of sample 1 and sample 2 and understand the pairing rules of DNA.

First, let's look at the given data: sample 1 is found to be 21% A, while sample 2 is 26% G.

Statement 1: "Sample 1 has a higher AT content than Sample 2."
To determine the AT content, we need to consider that in DNA, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). Since sample 1 has 21% A, it must also have 21% T to maintain the pairing rule. Therefore, the AT content of sample 1 is 21% + 21% = 42%. We do not have information about the G and C content of sample 1, so we cannot determine if it has a higher AT content than sample 2. Thus, statement 1 is inconclusive.

Statement 2: "Sample 1 is 29% T."
As we mentioned earlier, the AT content of sample 1 is 42%. Since sample 1 has 21% A, it must also have 21% T. Therefore, statement 2 is false.

Statement 3: "Sample 2 will melt at a lower temperature than Sample 1."
DNA melting temperature is influenced by its GC content. Higher GC content leads to a higher melting temperature. Since sample 2 has a higher G content (26%), it suggests a higher GC content (26% + 26% = 52%). In comparison, sample 1 had a lower GC content since we only know its A content (21%). Therefore, sample 2 will have a higher melting temperature than sample 1. Thus, statement 3 is false.

Statement 4: "Sample 1 is complementary to Sample 2."
For two DNA strands to be complementary, their base pairs must follow the pairing rule. In sample 1, we know it has 21% A, so it must also have 21% T. Correspondingly, since sample 2 has 26% G, it must have 26% C. The complementary base pairs between sample 1 and sample 2 are A-T and G-C. Thus, sample 1 is indeed complementary to sample 2. Therefore, statement 4 is true.

In conclusion, the only true statement is: "Sample 1 is complementary to Sample 2."